ABSTRACT Severe destructive behaviors (SDB) are fairly common among individuals with autism spectrum disorder (ASD). Functional Communication Training (FCT) is a commonly used reinforcement- based intervention for SDB. Although the majority of FCT research has focused on response- specific variables (i.e., effort) that affect outcomes, additional procedural variables have received increased attention. For example, researchers have evaluated the presence and impact of treatment relapse (i.e., resurgence) during FCT generalization. Furthermore, invariant responding may affect maintenance of therapeutic outcomes during FCT when treatment challenges are introduced (i.e., schedule thinning). The majority of research on invariant responding and resurgence is either translational in nature or has limited application for treatment. Thus, additional research is warranted. The aims of this project are to (a) identify functionally equivalent communication responses that will promote varied communication responding, (b) evaluate the effects of progressively leaner schedule requirements on varied communication, and (c) demonstrate that introducing multiple communication responses, and altering reinforcement schedules using principles of behavioral economics, will mediate invariant responding and the variables that relate to resurgence of SDB. The study includes 4 phases for the target group: (a) assessment of client preference and proficiency for communication responses, (b) an initial FCT intervention, (c) a progressive-ratio assessment, and (d) a treatment-challenge evaluation. Additionally, a comparison group will be exposed to phases a, b, and d. Thus, the comparison group will not be exposed to multiple communication responses or leaner schedules of reinforcement to further examine the effects of these variables on varied communication and resurgence of SDB.